Increasingly HIV prevention specialists are focusing efforts on community social mobilization (CSM) strategies as a powerful and sustainable means of combating the HIV epidemic. However, further conceptual development of CSM, including examination of the dimensions of mobilization and the means or pathways through which CSM encourages HIV prevention, is needed in the field, particularly among the most vulnerable populations in high prevalence countries. This study aims to improve the conceptual understanding of community social mobilization (Aim 1), examining the dimensions of mobilization as they relate to similar constructs within the South African context;create a measure of CSM that can be used to evaluate changes in CSM (Aim 2);and finally to test the CSM measure in a large representative survey of 1,200 people in 25 communities (Aim 3). This proposal will be conducted in conjunction with the NIMH funded study "Effects of cash transfer and community mobilization in young South African women," (1R01MH087118-01: PI, Pettifor) which includes a community social mobilization component to promote HIV prevention among young people. The conceptual development of CSM will be accomplished by conducting formative research, including focus group discussions (FGDs) and in-depth-interviews (IDIs) in order to adapt, refine, and enhance prior work conceptualizing the definition and dimensions of CSM to fit the rural South African context. We will generate a series of context specific items to measure CSM and pilot test the new measure among 100 young people in the R01 intervention communities. Finally, we will test the measure of CSM in the large scale baseline survey of the R01. The scale performance will be evaluated for reliability and validity during the pilot test and the baseline survey using both item response modeling and factor analysis on the survey data. Findings regarding conceptualization, dimensionality, and the scale items and scale performance will be published for use or adaptation in future HIV prevention initiatives. Identifying the dimensions of CSM, including context specific components, will permit better planning of future interventions, allow building improved measures of mobilization in a community, and, as a result, encourage more rigorous evaluations of CSM strategies. The parent R01 provides a unique opportunity to study the process, potential, and vital components of community social mobilization in a context where strides in prevention are critical. PUBLIC HEALTH RELEVANCE: This study aims to develop a conceptual definition and understanding of community social mobilization (CSM), examine of the dimensions of mobilization in the South African context, and to create a quantitative measure of CSM. This study will also test the CSM measure in a large representative survey of 1,200 young people in 25 South African communities, being implemented as part of the NIMH funded R01 "Effects of cash transfer and community mobilization in young South African women," (1R01MH087118-01: PI, Pettifor). Performing an in- depth examination of community social mobilization, furthering conceptual development and improving measurement of CSM will improve the design and evaluation of future mobilizing interventions, which are particularly important in high HIV prevalence settings.